1. Field of the Invention
The present invention relates to a friction disc clutch assembly adapted for use in automotive vehicles, and more particularly to an improvement of a clutch cover in the friction disc clutch assembly.
2. Description of the Prior Art
As shown in FIG. 10, a conventional friction disc clutch assembly comprises a flywheel 2 secured to a drive shaft 1, a clutch cover 4 integrally connected to the annular flange of flywheel 2 by means of a plurality of circumferentially spaced bolts 3, a pressure plate 5 mounted in the clutch cover 4 in such a manner as to be rotatable with and axially displaceable with respect to the flywheel 2, a diaphragm spring 6 mounted within the clutch cover 4 to bias the pressure plate 5 toward the flywheel 2, and a clutch disc 8 splined to a driven shaft 7 and interposed between the flywheel 2 and the pressure plate 5. The clutch disc 8 is integrally provided with a pair of clutch facings 9 for frictional engagement with the flywheel 2 and pressure plate 5. When pressed between the flywheel 2 and the pressure plate 5 under the biasing force of diaphargm spring 6, the clutch disc 8 acts to transmit rotational torque of the drive shaft 1 to the driven shaft 7 therethrough. When the biasing force of diaphragm spring 6 is released to retract the pressure plate 5, the clutch disc 8 is disengaged from the flywheel 2 to disconnect the torque transmission between the drive shaft 1 and the driven shaft 7. As shown in FIG. 9, the clutch cover 4 is formed approximately in an annular configuration and formed in its outer peripheral portion with an internal cylindrical surface 4a the radius r.sub.o of which is determined with center at the rotation axis X of the clutch assembly.
In general, the friction disc clutch assembly is contained within a housing which is formed with a vent hole for cooling the clutch assembly. During travel of the vehicle on muddy roads, the vent hole permits entrance of muddy water into the housing. The muddy water flows into the interior of clutch cover 4 through the central opening 6a of diaphragm spring 6 and is splashed radially outwardly due to a centrifugal force acting thereon. As a result, the muddy water is splashed onto the internal cylindrical surface 4a of clutch cover 4 and deposited there as illustrated by cross-hatching M in the figure. The deposit of muddy water causes trouble in axial displacement of the pressure plate 5, resulting in insufficient disengagement of the clutch assembly. If the deposited mud falls between the pressure plate 5 and the facings 9 of clutch disc 8, there will occur slippage of the clutch assembly and unexpected defacement of the clutch facings 9 in a short period of time.